In many light emitting arrangements comprising a solid state light source, e.g. an LED, the solid state light source is encapsulated by a transparent material in order to increase the light extraction of the arrangement and to protect the solid state light source. It is important to use a high refractive index material, e.g. silicones, with a high photochemical stability as encapsulant. The encapsulant comprising the high refractive index material may increase the system efficiency considerably if used in a component, e.g. a wavelength converting member or a transparent cover member, of such light emitting arrangements.
Nanocrystals have been proposed to be dispersed into a matrix of high refractive index material, such as a polymer matrix, e.g. a silicone matrix, in order to increase the refractive index of the matrix further. The nanocrystals are typically prepared and surface-modified before being dispersed into the matrix. The nanocrystals are surface-modified in order to enhance compatibility with the high refractive index material of the matrix. However, this method tends to give rise to excess light scattering due to aggregation of the nanocrystals.
US 2012/0068118 A1 addresses the problem of undesirable light scattering, and proposes a matrix doped with semiconductor nanocrystals which comprise ligands that allow for mixing with various matrix materials, including polymers, such that a minimal portion of light is scattered. A composition that comprises a nanostructure, and a polymeric ligand bound to the surface of the nanostructure is disclosed. The ligand comprises a linear silicone backbone, and one or more nanostructure binding moieties coupled to the silicone backbone.
Still, however, there is a need in the art for high refractive index compositions with further reduced excess light scattering. There is also a need in the art for improved methods of preparation of high refractive index compositions with reduced excess light scattering.